The Role of Lateral Retinacular Release in Preventing Patellofemoral Malalignment in Double-Bundle Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

The study was granted ethical approval of Faculty of Medicine Universitas Indonesia Ethical Committee (No. 758/UN2.F1/ETIK/2014). Participants of this study received oral and written information about the study, after which written consent was obtained.

Between January 2018 and December 2019, a total of 100 patients who were to undergo arthroscopic ACLR were enrolled in a prospective randomized controlled study. All ACL reconstructions were conducted by the same surgeon (LAP).

Indication of the surgery was an acute or chronic isolated ACL rupture. Inclusion criteria were as follow: (1) unilateral isolated complete ACL rupture; (2) age, 16–40 years; (3) normal body mass index (BMI: 18.5–24.9 kg/m²); (4) signs and symptoms in physical examination consistent with the diagnosis of ACL rupture and magnetic resonance imaging (MRI) indicating ACL injury (MRI 3.0-Tesla Magnetom Skyra; Siemens Medical Solutions, Malvern PA, USA); and (5) no previous surgery in the index knee. The exclusion criteria were (1) existence of flexion contracture more than 20°, (2) presence of anterior knee pain prior surgery, (3) Q angle > 14° in males and > 17° in females, (4) presence of patellar tilting (positive J-sign), and (5) muscular dysfunction (Medical Research Council scale for muscle strength < 5).

Patients were randomized to undergo SB-ACLR (group 1, n = 30), DB-ACLR (group 2, n = 30), or DB-ACLR with concomitant LR (group 3, n = 40) (Fig. 1). Randomization was performed by one of the authors (TSE) using the block randomization technique with use of an online randomization generator (http://www.graphpad.com/quickcalcs) and another author (IHD) assigned participants to interventions.

Fig. 1
Schematic chart of the patient enrollment.

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Surgical Technique

Standard medial and lateral arthroscopic portals were established adjacent to the patellar tendon prior to routine diagnostic arthroscopy to confirm the diagnosis of ACL tear and find any concurrent injuries. All reconstructions were performed with hamstring autografts.

SB-ACLR

The tibial tunnel was first created by drilling at the center of the ACL footprint. Meanwhile, the femoral tunnel was created by drilling at the anatomic anteromedial bundle through the anteromedial portal, while the knee was in 120° flexion position. After all tunnels were created, the graft was pulled through the tibial tunnel into the femoral tunnel. Graft fixation was done with suspensory fixation (Endobutton; Smith & Nephew, Andover, MA, USA) and bioabsorbable interference screws (Biosure, Smith & Nephew) for the femoral site and tibial site, respectively. The graft was then tensioned with the knee in slight flexion before fixation at the tibial tunnel.

DB-ACLR

The anteromedial bundle and posterolateral bundle attachments in the femoral site were identified with a guide-wire through a far anteromedial portal. The anteromedial and posterolateral bundles were determined according the resident’s ridge. In the sagittal plane, tunnels for the anteromedial bundle and posterolateral bundle were placed 3 mm posterior to the resident’s ridge.10) Bone tunnels for the anteromedial and posterolateral bundles were drilled over the guide wire when the knee was flexed greater than 120°. The tibial tunnels were created using two 2.4-mm guide wires inserted into the center of the anteromedial and posterolateral bundle footprints. Graft passage and fixation were performed similar to SB-ACLR.

LR

The lateral retinaculum release was performed through the suprapatellar portal as a viewing portal following the DB-ACLR. The radiofrequency ablator (Arthrocare, Mitek; Depuy, Raynham, MA, USA) was used to perform the release continuously through the capsule and the lateral retinaculum extending from and including the vastus lateralis tendon to the joint line, passing approximately 1–1.5 cm lateral to the patella (Fig. 2). After the lateral retinaculum release was performed, the patella trajectory was evaluated to ensure the patella was tracking at the center of the trochlea.

Fig. 2
Arthroscopic lateral release (LR) performed using a lateral suprapatellar portal. (A) Before LR. (B) During LR. (C) After LR.

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Outcome Assessment

Functional outcome

The functional outcomes of the patients were evaluated by an orthopedic surgeon who did not participate directly in the surgery (JF). The Kujala score, which consists of 13 knee-specific questions, is commonly used to evaluate patellofemoral joint pain. Patient’s responses on patellofemoral joint-related disorders were assessed according to the scores including walking, running, jumping, stair climbing, squatting, swelling, and knee stiffness. Preoperative and 6-month postoperative scores were compared between groups.

Radiologic outcome

Preoperative tibial tubercle-trochlear groove (TTTG) distance was measured between the tibial tuberosity and the deepest point of the trochlear groove on an axial T2-weighted MRI 3.0T Magnetom Skyra (Siemens Medical Medical Solutions, Malvern, PA, USA) in supine position.11) According to Pandit et al.,10) the normal value for TTTG in men and women is 10 ± 1 mm. In the current study, we used the technique suggested by Pandit et al.10) by first measuring the midpoint of the distal insertion of the patellar tendon at the tibial tuberosity and then the images were scrolled proximally to the first image that depicted a complete cartilaginous trochlear groove. A reference line at the posterior femoral condyles was drawn and a second line from the deepest point of the trochlear groove perpendicular to this reference line was marked. Another line was drawn perpendicular to the reference line and the distance between these two perpendicular lines was measured as TTTG (Fig. 3). The radiological evaluation of the patients was performed by an orthopedic surgeon who did not participate directly in the surgery (EK). Preoperative and postoperative TTTG distance were compared between groups.

Fig. 3
Measurement of the tibial tubercle-trochlear groove (TTTG) distance11) in the magnetic resonance imaging axial view. The TTTG distance is measured by creating a line (vertical yellow line) along the trochlear groove at the midpoint of a projected reference line connecting two femoral condyles (A) and a second line (red line), which is drawn parallel to the first line at the most anterior part of the tibial tubercle (B). (C) TTTG is the distance between these two parallel lines (yellow line-red line), which represents tibial rotation in relation to the femur.

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The most important finding in this study is that a relatively simple procedure added substantial benefit to the success of ACLR. Lateral retinacular release has been long performed indiscriminately to treat patellofemoral joint problems with conflicting results.13, 14, 15) Theoretically, LR relieves abnormal posterior and lateral tethering of the patella that may lead to lateral tilt and subluxation. A shortened lateral retinaculum will result in excessive pressure on the lateral facet of the patella because when the knee flexes, the iliotibial band is drawn posteriorly and this will eventually cause cartilage degeneration on the overloaded lateral facet.16) Additional LR following a primary total knee arthroplasty (TKA) procedure in a tight retinaculum has been proven to correct patellar maltracking that often causes anterior knee pain after TKA.17)

It has been reported that PFPS after ACLR is commonly the major cause of anterior knee pain, preventing patients’ return to sports.18) Patellofemoral malalignment is commonly the main source of PFPS after an ACLR, causing an imbalance of the extensor mechanism and excessive pressure on the patellofemoral joint, and it may result in cartilage damage.19, 20)

The TTTG distance is a measure of lateralization of the tibial tuberosity in relation to the femoral trochlea. Many studies have confirmed that lateralization of the tuberosity is linked to patellar instability, hence TTTG is an important parameter for patellofemoral disorders.11, 12) The normal TTTG value is 10 ± 1 mm according to Pandit et al.10) The mean preoperative TTTG value in this study was between 10.9 and 13.82, indicating a more internally rotated tibia, which is commonly found in ACL-deficient patients according to Saper et al.16)

Several techniques have been developed to overcome patellofemoral malalignment after ACLR. The previous trend was to perform anatomic, independent femoral drilling reconstructions, resulting in a more oblique disposition of the graft and improved rotational control.21, 22) Unfortunately, residual pivot-shift is still high with this technique. Another technique promotes anterolateral tenodesis and recently the reconstruction of the anterolateral ligament has attracted increasing attention.23, 24) However, the proper anatomic insertions of the ligament are not clear and controversial results are described in the literature, such as compromised range of motion in case of improper placement.

A recent study of Kidera et al.21) showed that DB-ACLR also improved tibial rotational instability during squatting motion using the two-dimensional/three-dimensional registration technique. However, there are many literatures showing considerable controversy regarding the SB versus DB graft, showing equivocal results in terms of reducing tibial rotation.6, 22, 23, 25) In an isolated total ACL tear, there was rotational laxity causing patellofemoral maltracking, which can be proven on an internally rotated tibial tubercle relative to the trochlea groove or negative TTTG. In this study, postoperatively there was a significant decrease in TTTG endorotation in groups 2 and 3.

The lowest TTTG value was observed in patients in group 3 (6.7 ± 4.69) compared to group 2 (9.1 ± 4.83) and group 1 (11.74 ± 1.76) (p = 0.030). This result shows that although both DB and DB-LR procedures decrease TTTG endorotation significantly, DB-LR will decrease the TTTG distance more, albeit not statistically significant. The preoperative TTTG value showed an increase in internal rotation due to the loss of anterolateral stability produced by the torn ACL. The DB-LR group showed superiority in decreasing the TTTG value compared to other groups and also improving the Kujala score significantly compared to other groups (p = 0.003).

Arthroscopic LR procedure is not a new procedure; however, simultaneous performance with ACLR has never been reported. The idea to overcome internal rotational laxity after ACLR through patellofemoral realignment was either performing a lateral advancement of the tibia or releasing the patella, rendering its medial translation, hence creating patellofemoral realignment. Our study showed that DB-LR ACLR, when performed in isolated ACL ruptures, increased TTTG scores preoperatively and prevented PFPS within a period of 6–18 months postoperatively.

We recommend a simple, cheap, and safe technique to overcome PFPS by combining two well performed techniques, which were first introduced worldwide with quite satisfactory outcome. However, this study has several drawbacks including the lack of postoperative patellofemoral chondral evaluation, functional score analysis with longer duration of follow-up and larger sample, and long-term effect of LR such as pain and muscle weakness. Intraoperative objective measurement of LR needs to be studied in order to obtain a more optimum result. The current study was also presented with the 6-month follow-up period, which necessitates further research with a longer follow-up period. Concomitant lateral retinacular release in ACLR significantly improved the Kujala score compared to ACLR without LR; therefore, LR may serve as a valuable option to overcome PFPS in ACLR.